1. Field of the Invention
The invention relates to a method for the automatic dynamic dosing at least of one liquid component of a mixed liquid, particularly of the hardener of a 2K-lacquer with mother lacquer, with which the flow of the pressure-transported main component (mother lacquer) is measured and the flow of the pressure-fed secondary component (hardener) which is to be dosed is regulated and moreover adjusted corresponding to the predetermined quantity ratio of the two components to be mixed; as well as a device for performing of such a method with each one pressure vessel containing the main component and the secondary component, respectively; with an analog measuring transducer which produces an electrical value proportional to the flow of the main component; with a geared pump for feeding of the secondary component to a servo controlled member or system; with an electrical machine, which is operatable as a motor and drives the geared pump, which pump forms a regulating element with the electrical machine; with an electronic four-quadrant controller for the electric machine; with a digital potentiometer for adjusting or controlling the quantity ratio of the main component relative to the secondary component; and with an electrical arrangement with which the measuring transducer is connected to a controller and the electrical machine for the secondary component as well as the controller therefor are arranged in an electrical automatic control circuit.
2. Description of the Prior Art
A device of this type by which the geared pump alternately or reciprocally serves for throttling of the secondary component and for this purpose the electrical machine is operatable as a generator braking the pump, and a method of the introductory type which is performable with it, are known from the editions 1976 Oberflaeche No. 6, pages 342 to 344 and JOT, June 1976, pages 19 to 21. Accordingly for "controlling" the quantity of the main component there is used a "regulating element" which should comprise the pressure vessel for the main component and the throttle in a spray gun which is connected to the device for atomization of the mixed liquid by means of compressed air. Obviously it does not deal with the control of the flow of the main component by means of a controller on an automatic control system, but rather merely to the control of the flow of the main component by means of a regulating element on a servo control member or system, whereby also the designation control chain may be used.
The known device has two continuously working measuring cells of unknown construction type; one of which constitutes a measuring transducer and the other is arranged in the control system for the secondary components downstream of the regulating member for the secondary component and the controller for the secondary component supplies the control value (actual value) of the flow of the secondary component, while the measuring transducer in connection with the potentiometer for the adjustment of the quantity ratio of the main component and the secondary component supplies to the controller for the secondary component a desired value of the flow of the secondary component, which desired value is proportional to the measured flow of the main component.
with respect to the exact maintainance of the predetermined quantity ratio of the two components which are to be mixed, the combined control and regulation of the flow of the secondary component indeed brings a better result than the pure control of the flow of the secondary component with the help of the measured flow of the main component. It is however to be determined that possible pressure oscillations in the pressure vessel for the main component as well as in the path portion between the regulating element for the secondary component and the measuring cell for the secondary component, indirectly and directly, respectively, negatively influence the precision of the dosing of the secondary component. It is consequently desireable to increase to precision of the dosing by means of completing and/or modifying measures.
The invention consequently is based on the task to provide a method of the introductory named type and to make a device of the introductory named type which is suited and determined for its performance, by which a higher dosing precision is achieved.